JPH06224716A - Multi-point signal selection device - Google Patents

Abstract

PURPOSE:To reduce a measurement error caused by a leakage current or high frequency noise by connecting changeover switches to a signal processing system or an earth potential point selectively while interlocking with the driving signal of each signal selecting means. CONSTITUTION:Each of moving contacts (a) of changeover switches SW1-SWn is driven while interlocking with ON/OFF drive of signal selecting means AS 1-ASn. That is, when the signal selecting means AS1-ASn are turned on, each of moving contacts (a) is connected to the position of each of fixed contacts (b) and when the signal selection means AS1-ASn are turned off, each of moving contacts (a) is connected to the position of each of fixed contacts (c). When a signal system connected to an input terminal IN1 is measured, only the signal selection means AS1 is turned on, the other signal selection means AS2-ASn are turned off, only the moving contact (a) of the changeover switch SW1 is connected to its fixed contact (c) and each of moving contacts (a) of the other changeover switches AS2-ASn is connected to its fixed contact (c). Thus, an input signal given to the input terminal IN 1 is inputted to an attenuator ATT and the leakage current or high frequency noise of the other system flows to an earth potential point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-point signal selection device, and more particularly to an analog input caused by a capacitance between input and output of a semiconductor switch in a multi-point signal selection device using a high voltage semiconductor switch. It is related to the reduction of the error of.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing an example of an input block of a multipoint measuring device such as a recorder. In the figure, IN1 to INn are input terminals corresponding to a plurality of measurement channels and are connected to the multiplexer MPX. The multiplexer MPX has these input terminals IN1 to I
Any analog signal input to Nn is selectively input to the attenuator ATT. The output signal of the attenuator ATT is applied to the A / D converter ADC via the preamplifier PA, converted into a digital signal, and applied to a signal processing unit (not shown).

As such a multiplexer MPX, a multiplexer switch matrix having a high breakdown voltage (for example, about 1500 V) is used. FIG. 3 is a circuit diagram showing an example of such a semiconductor switch.
In the figure, reference numeral 1 denotes a light emitting diode which is selectively driven, and the output light thereof is detected by a light receiving element 2 formed of a plurality of photodiodes connected in series. FETs 3 and 4
The switching element is composed of the following elements, and is connected so as to be simultaneously turned on and off by the detection output of the light receiving element 2. That is, the anodes of the light receiving elements 2 connected in series are connected to the gates of the switching elements 3 and 4,
The cathode of the light receiving element 2 connected in series is connected to the connection point of the source S of the switching element 3 and the source S of the switching element 4.

In such a structure, assuming that an analog signal is input to the drain D of the switching element 3, the switching elements 3 and 4 are simultaneously turned on by selectively driving the light emitting diode 1 to light. As a result, an analog signal is output to the drain D of the switching element 4. Figure 4 shows the multiplexer MP
4 is a circuit diagram showing an example of X, and is a semiconductor switch A of FIG.
S is shown as a mere switch. 1C in FIG.
Since three signal lines are provided for each measurement channel of H to 30CH, three semiconductor switches AS are provided for each measurement channel. And 1CH to 10CH, 11
CH to 20CH and 21CH to 30CH are divided into groups G1 to G3, respectively, and the output signal lines L1 to L3 of the groups G1 to G3 are directly connected to the common signal line L0.

[0005]

However, in such a conventional configuration, it is assumed that the measurement channel CH1 to which the analog signal of the voltage Va is input is selected and the other measurement channels are turned off. , The voltage Va is also applied to the output side of a total of 29 sets of switches of the respective measurement channels that are turned off via the common signal line L0 and the output signal lines L1 to L3, and the capacitance between the input and output of the semiconductor switch is As well as charging, the drain and the capacitance between the drains in FIG. 3 are also charged. Then, the electric charge charged in each switch of each measurement channel is discharged when the measurement channel is switched and no voltage is applied.

For example, when the measurement channel CH2 is subsequently selected, the error voltage V given to the measurement channel CH2 by the discharge current is as follows. The ON resistance of the switch of the measurement channel CH2 is R, the discharge current of each measurement channel is i, and the discharge current is If the number of measurement channels affected by is N, then V = R × i × N. Here, in the case of FIG. 4, N = 28, which adversely affects the measurement result of the analog input signal of each measurement channel.

Further, since the semiconductor switch has the input-output capacitance as described above, when high frequency noise is applied to the input terminal of the measurement channel in which the switch is off, this noise passes through the switch. There is also a problem that the measurement error may flow into another measurement channel whose switch is turned on. The present invention solves these conventional problems, and an object of the present invention is to realize a multipoint signal selection device with a small measurement error caused by leak current or high frequency noise.

[0008]

A multipoint signal selection device according to the present invention comprises a plurality of signal selection means composed of high-voltage semiconductor switches for selecting a signal system to be measured, and an output side of each of these signal selection means. And a plurality of change-over switches which are connected to each other and selectively connect to a signal processing system or a ground potential in association with a driving state of each signal selecting means.

[0009]

[Function] Only the output side of the high withstand voltage semiconductor switch that is turned on is connected to the signal processing system via the changeover switch, and the output side of the other high withstand voltage semiconductor switch that is turned off is passed through the changeover switch. Connected to earth potential.
As a result, the leak current and high frequency noise of the system of the high breakdown voltage semiconductor switch that is turned off flow to the ground potential, and the measurement error due to the leak current and high frequency noise can be improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The same reference numerals are given to the same portions as. In FIG.
Each of the output sides of the plurality of signal selecting means AS1 to ASn, which are semiconductor switches having high withstand voltage and which constitute the multiplexer MPX for selecting the signal system to be measured, selectively outputs a signal in association with the driving state of each signal selecting means. A plurality of changeover switches SW1 to SWn connected to the processing system or the ground potential are connected. That is, the changeover switches SW1 to SW
The n movable contacts a correspond to the corresponding signal selecting means AS1 to ASn.
The fixed contact b is connected to the signal processing system (not shown) through the attenuator ATT, and the fixed contact c is connected to the ground potential. In addition,
As the changeover switches SW1 to SWn, for example, semiconductor switches having a withstand voltage of about 100 V may be used, or ones having mechanical contacts may be used.

In such a structure, the changeover switch S
The movable contacts a of W1 to SWn are signal selecting means AS1 to A
Switching driving is performed in conjunction with on / off driving of Sn. That is, when the signal selecting means AS1 to ASn are turned on, they are connected to the fixed contact b side, and when the signal selecting means AS1 to ASn are turned off, they are connected to the fixed contact c side. FIG. 1 shows a state in which the signal system of the input terminal IN1 is measured, and only the signal selecting means AS1 is turned on and the other signal selecting means AS is turned on.
2 to ASn are turned off, only the movable contact a of the changeover switch SW1 is connected to the fixed contact b, and the other changeover switch S
The movable contacts a of W2 to SWn are connected to the fixed contact c.

As a result, the input signal of the input terminal IN1 is input to the attenuator ATT via the signal selecting means AS1 and the changeover switch SW1 and the other input terminals IN2 to IN2.
The leak current and high frequency noise of the INn system flow to the ground potential, and the influence of the leak current and high frequency noise of the system of the other input terminals IN2 to INn on the input signal of the input terminal IN1 can be removed.

In the above embodiment, 30 channels are set to 1
Although the example of dividing into three groups of 0 channels has been described, these numbers can be changed as appropriate.

[0014]

As described above, according to the present invention,
It is possible to realize a multi-point signal selection device with a small measurement error due to a leak current of a high-voltage semiconductor switch and high-frequency noise from the outside.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an example of an input block of a multipoint measuring device.

FIG. 3 is a circuit diagram showing an example of a semiconductor switch.

FIG. 4 is a circuit diagram showing an example of a conventional multiplexer.

[Explanation of symbols]

 1 Light emitting diode 2 Light receiving element (photodiode) 3, 4 Switching element (FET) AS Semiconductor switch (signal selection means) SW changeover switch

Claims (1)

[Claims] 1. A plurality of signal selecting means composed of high-voltage resistant semiconductor switches for selecting a signal system to be measured, and connected to each output side of these signal selecting means, interlocking with a driving state of each signal selecting means. A multipoint signal selection device comprising: a plurality of changeover switches selectively connected to a signal processing system or a ground potential.